Does habitat fragmentation promote climate-resilient phenotypes?

Understanding how individual differences in physiological performance modify behavioral responses to environmental variability and its fitness consequences is key to predicting the vulnerability of species and populations to environmental change. For many species, summit metabolic rate (M); the upper limit to heat production) and basal metabolic rate (BMR; the lower limit related to energy acquisition and processing) often constrain aspects of physiological performance and behavioral activity. We examined the relationship between metabolic phenotypes, foraging behavior, and survival in overwintering black-capped chickadees (Poecile atricapillus) inhabiting contiguous and fragmented forested landscapes. We found that birds with lower summit metabolic rates were generally more sensitive to winter weather and increased their use of supplemental feeding stations as ambient temperatures decreased. In highly fragmented forests, this relationship may have incurred strong survival consequences, as birds with lower summit metabolic rates were less likely to survive the winter season. Additionally, we found that chickadee populations persisting in fragmented landscapes were characterized by slightly higher thermogenic capacity (M) and lower maintenance metabolic costs (BMR). We conclude that habitat loss and fragmentation present unique selection pressures that alter the relationships between environmental variability, behavior and physiology, and result in context-specific fitness consequences

解析生理表现的个体差异如何调控动物对环境波动的行为响应及其适合度后果，是预测物种与种群对环境变化脆弱性的核心所在。对多数物种而言，最大代谢率（summit metabolic rate, M，即产热上限）与基础代谢率（basal metabolic rate, BMR，即与能量获取和处理相关的代谢下限）通常会限制其生理表现与行为活动的多个维度。本研究针对栖息于连续与破碎化森林景观中的越冬黑头山雀（Poecile atricapillus），探究了代谢表型、觅食行为与存活率之间的关联。研究结果显示，最大代谢率较低的个体通常对冬季气候更为敏感，会随着环境温度降低而更频繁地利用人工补饲站点。在高度破碎化的森林中，该关联可能会带来显著的存活适应性后果——最大代谢率较低的个体越冬存活率更低。此外，本研究还发现，在破碎化景观中存续的黑头山雀种群，其产热能力（即最大代谢率M）略高，而维持代谢成本（即基础代谢率BMR）更低。综上，生境丧失与破碎化会形成独特的选择压力，改变环境波动、行为与生理之间的关联，并带来情境特异性的适合度后果。